Química de igarapés de água preta do nordeste do Amazonas - Brasil

Abstract

Neste estudo foram analisados pH, Eh, condutividade elétrica, cloreto, sílica, fosfato, K, Na, Ca, Mg, Fe, F, Zn, Ni, Co, Mn, Pb, Cu, Cr, Li e Cd nas águas de drenagens de pequeno porte no nordeste do Amazonas. As águas são pretas, predominantemente ácidas e levemente redutoras e com baixo conteúdo de elementos dissolvidos. Contudo, a química indica que são heterogêneas e refletem o ambiente geológico por onde percolam. SiO 2 , Na e K são os constituintes mais abundantes na fase dissolvida, especialmente nas drenagens mais a norte pertencentes as bacias do Uatumã, Urubu e no igarapé Canoas que drenam as rochas da Suíte Intrusiva Água Branca e Mapuera e as sedimentares do Grupo Iricoumé e as Formações Prosperança, Nhamundá, Manacapuru, Pitinga Os igarapés menores, que drenam exclusivamente os sedimentos da Formação Alter do Chão, são os mais diluídos. Os elementos-traços analisados estão em concentrações muito baixas. PalavRaS chavE: afluentes do Amazonas, estiagem; carga dissolvida Chemical composition of black water creeks from northern of AmazonasBrasil aBSTRacTThe present study analyzed pH, Eh, electric conductivity, chloride, silica, phosphate, K, Na, Ca, Mg, Fe, Zn, Ni, Co, Mn, Pb, Cu, Cr, Li and Cd in draining waters making part of smaller creeks located in the northeastern Amazonas State. The waters have black colour, are predominantly acid and slightly reductive and have low content in dissolved elements. Otherwise they are chemically heterogeneous and reflect the geological environment. The SiO 2 , Na and K are the most abundant dissolved constituents, especially on the drainages farther north belonging to Uatumã, Urubu basins and Canoas Stream, which drain the rocks of Água Branca and Mapuera Intrusive Suite, Iricoumé Group and Prosperança, Nhamundá, Manacapuru, Pitinga Formations. Smaller Streams, which drains Alter do Chão Formation sediments, exclusively, are the most diluted ones. The analysed trace elements present very low concentrations.

Distribution of Metals in the Waters and Sediments of Rivers in Central Amazon Region, Brazil

“…Fe and total Al concentrations in water samples were observed in the dry and rainy seasons, with certain values exceeding the legislated limits in some localities and these elements are usually naturally present in the soil. 2 The Fe concentration ranged similiarly with the results previously reported, indicating the concentrations of this element are from natural sources. 2 Concentrations of total and dissolved Fe had highest values during the dry period and some sites exceeded the recommended legal values (Table 3).…”

“…Overall, the results obtained are in accordance with another Amazon freshwater studies. 2,11 Total Cr, Ni, Cd, Cu, Pb, Fe and Al concentrations varied as described in Table 3: in the dry period, the total Cr concentrations were < 2.78 μg L -1 for most of locations, except for whitewater rivers Amazonas 1 and Madeira, 7.67 and 10.29 μg L -1 , respectively, and for blackwater rivers Anebá and Urubu 2, with concentrations of 13.15 and 5.58 μg L -1 , respectively.…”

“…In the Amazon, three types of waters can be identified: whitewaters with near-neutral pH and that contain large amounts of particulates; blackwaters that are acidic and rich in organic matter; and clear waters that have physicochemical characteristics between white and blackwater rivers. [1][2][3] Amazonas River is among the world's largest in terms of drainage area (6 × 10 6 km 2 ), with 20% of the flow of water from the land to the ocean. Itacoatiara is the third most populous municipality in the State of Amazonas, with an area of 8,891,906 km 2 and a hot, rainy and humid climate.…”

“…6 Several studies of metal transport have been conducted in the Amazon region, but most have been centered on the main rivers, especially the Negro, Solimões, Madeira and Amazonas River. 2,3,[7][8][9][10][11][12][13] Considering the land use in this region and since the Amazon River carries annually around 600 million tons of sediment to the ocean, the evaluation of metals transportation in the main tributaries of white and blackwaters from under-investigated regions are of great relevance to monitor the vulnerability of aquatic life and because these shall contribute to a significant fraction of metals exported to the ocean. This study aimed determination of total, dissolved and particulate metals concentration in freshwater and sediments of the rivers from Central Brazilian Amazon.…”

Copper toxicity for Scinax ruber and Rhinella granulosa (Amphibia: Anura) of the Amazon: Potential of Biotic Ligand Model to predict toxicity in urban streams

“…Typically, black water is found in the Rio Negro that has low pH, low conductivity and low concentrations of cations (Silva et al 1999;Horbe and Oliveira 2008). However, in urban areas under intense anthropic pressure, these characteristics are altered to increased pH, high turbidity, reduced dissolved oxygen concentrations, increased concentrations of calcium, magnesium, sodium, potassium, sulfate and bicarbonate, and high concentrations of transition metals (Silva et al 1999;Melo et al 2005;Nascimento and Silva 2010).…”